School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510275, China.
School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
J Hazard Mater. 2020 Jul 5;393:122390. doi: 10.1016/j.jhazmat.2020.122390. Epub 2020 Feb 24.
Iron oxide nanoparticles (IONPs), commonly occurring in soils, aquifers and subsurface sediments, may serve as important electron shuttles for the biotransformation of coexisting toxic metals. Here, we explored the impact of different IONPs (low-crystallinity goethite and ferrihydrite, high-crystallinity magnetite and hematite) on the reduction of Cu(II) by Geobacter sulfurreducens and the associated electron shuttle mechanisms. All four IONPs tested can function as electron shuttles to enhance long distance electron transfer from bacteria to Cu(II). Upon IONPs addition, the rate of Cu(II) reduction increased from 14.9 to 65.0-83.8 % in solution after 7 days of incubation. Formation of both Cu(I) and Cu(0) on the iron oxide nanoparticles was revealed by the X-ray absorption near-edge spectroscopy. The IONPs can be utilized as conduits by bacteria to directly transfer electrons and they can also reversibly accept and donate electrons as batteries through a charging-discharging cycle to transfer electron. The latter mechanism (geo-battery) played an important role in all four types of IONPs while the former one (geo-conductor) can only be found in the magnetite and hematite treatments due to the higher crystallinity. Our results shed new light on the biogeochemically mediated electron flux in microbe-IONPs-metal networks under anaerobic iron-reduction conditions.
氧化铁纳米颗粒（IONPs）普遍存在于土壤、含水层和地下沉积物中，可能作为共存有毒金属生物转化的重要电子穿梭体。在这里，我们研究了不同的 IONPs（低结晶度针铁矿和水铁矿、高结晶度磁铁矿和赤铁矿）对脱硫弧菌还原 Cu(II)的影响及其相关的电子穿梭机制。四种测试的 IONPs 均可作为电子穿梭体，增强细菌向 Cu(II)的长距离电子转移。在 IONPs 添加后，在 7 天的孵育期后，溶液中 Cu(II)的还原速率从 14.9%增加到 65.0-83.8%。X 射线吸收近边光谱揭示了在氧化铁纳米颗粒上形成了 Cu(I)和 Cu(0)。IONPs 可以被细菌用作直接传递电子的导管，它们也可以通过充电-放电循环作为电池可逆地接受和提供电子，以传递电子。在后一种机制（地质电池）中，四种类型的 IONPs 都发挥了重要作用，而在前一种机制（地质导体）中，由于结晶度较高，只能在磁铁矿和赤铁矿处理中找到。我们的结果为在厌氧铁还原条件下微生物-IONPs-金属网络中生物介导的电子通量提供了新的认识。
